1. Field of the Invention
The present invention relates to an electrophotographic photoconductor, more particularly to an electrophotographic photoconductor comprising an electroconductive substrate and an electroconductive layer formed thereon comprising a pyrenylamine derivative, which is useful as an organic photoconductive material for use in the above-mentioned electrophotographic photoconductor and as a fluorescent whitening agent, an aldehyde compound serving as an intermediate for producing the pyrenylamine derivative, and methods for preparing the pyrenylamine derivative and the aldehyde compound.
2. Discussion of Background
Conventionally, inorganic materials such as selenium, cadmium sulfide and zinc oxide are used as photoconductive materials for electrophotographic photoconductors in the electrophotographic process. The above-mentioned electrophotographic process is one of the image forming processes, through which the surface of the photoconductor is charged uniformly in the dark to a predetermined polarity, for instance, by corona charge. The uniformly charged photoconductor is exposed to a light image to selectively dissipate the electrical charge of the exposed areas, so that a latent electrostatic image is formed on the photoconductor. The thus formed latent electrostatic image is developed by toner particles comprising a coloring agent such as a dye or a pigment, and a binder agent such as a polymeric material, to a visible image.
Fundamental characteristics required for the photoconductor for use in such an electrophotographic process are: (1) chargeability to an appropriate potential in the dark, (2) minimum dissipation of electrical charge in the dark, and (3) rapid dissipation of electrical charge when exposed to light.
However, while the above-mentioned inorganic materials have many advantages, they have several shortcomings from the viewpoint of practical use.
For instance, a selenium photoconductor, which is widely used at present, satisfies the above-mentioned requirements (1) to (3) completely, but it has the shortcomings that its manufacturing conditions are difficult, and accordingly, its production cost is high. In addition, it is difficult to work it into the form of a belt due to its poor flexibility, and it is so vulnerable to heat and mechanical shocks that it must be handled with the utmost care.
A cadmium sulfide photoconductor and a zinc oxide photoconductor can be obtained by coating a dispersion of cadmium sulfide particles and zinc oxide particles respectively in a binder resin on a substrate. However, they are poor in mechanical properties, such as surface smoothness, hardness, tensile strength and wear resistance. Therefore, they cannot be used in the repeated operation.
In order to solve the problems of the inorganic materials, various electrophotographic photoconductors employing organic materials have been proposed recently and some are put to practical use. For example, there are known a photoconductor comprising poly-N-vinylcarbazole and 2,4,7-trinitrofluorene-9-one, as disclosed in U.S. Pat. No. 3,484,237; a photoconductor prepared by sensitizing poly-N-vinylcarbazole with a pigment of pyrylium salt, as disclosed in Japanese Patent Publication 48-25658; a photoconductor comprising as the main component an organic pigment, as disclosed in Japanese Laid-Open Patent Application 47-37543; a photoconductor comprising as the main component an eutectic crystal complex of a dye and a resin, as disclosed in Japanese Laid-Open Patent Application 47-10735; a photoconductor prepared by sensitizing a triphenylamine compound with a sensitizer pigment, as disclosed in U.S. Pat. No. 3,180,730; a photoconductor comprising an amine derivative as a charge transporting material, as disclosed in Japanese Laid-Open Patent Application 57-195254; a photoconductor comprising poly-N-vinylcarbazole and an amine derivative as charge transporting materials, as disclosed in Japanese Laid-Open Patent Application 58-1155; a photoconductor comprising a polyfunctional tertiary amine compound, in particular benzidine compound, as a photoconductive material, as disclosed in U.S. Pat. No. 3,265,496, Japanese Patent Publication 39-11546 and Japanese Laid-Open Patent Application 53-27033; a photoconductor comprising a stilbene derivative, as disclosed in Japanese Laid-Open Patent Applications 58-198425 and 58-189145; and a photoconductor comprising a triarylamine derivative, as disclosed in Japanese Laid-Open Patent Application 58-65440.
These electrophotographic photoconductors have their own excellent characteristics and considered to be valuable for practical use. With various requirements of the electrophotographic photoconductor in electrophotography taken into consideration, however, the above-mentioned conventional electrophotographic photoconductors cannot meet all the requirements in electrophotography.